Pray simply. Do not expect to find in your heart any remarkable gift of prayer. Consider yourself unworthy of it. Then you will find peace. Use the empty cold dryness of your prayer as food for your humility. Repeat constantly: I am not worthy; Lord, I am not worthy! But say it calmly; without agitation.
Prayer demands that the mind should be pure of all thought and should admit nothing not belonging to prayer, even if it were good in itself. As if inspired by God the mind should withdraw from all things and hold its converse with Him alone.
Prayers at home are an introduction, a preparation for prayers in Church. Thus he who is not accustomed to pray at home can seldom pray diligently in Church. Experience bears witness to this: anyone can observe it for himself.
Prayer is a great good if offered up from a thankful soul; if we are steadfast in it, so that whether we receive or do not receive what we pray for we at all times give thanks to God. For since He will sometimes grant what we ask and sometimes will not, in both cases it is to our gain... For oftentimes God will delay, not as denying our prayer, but in His wisdom seeking rather for our perseverance, and desiring to draw us nearer to Himself; as a loving father when asked by his son for something will often do; withholding consent, and not from the will to refuse, but rather to encourage him in steadfastness.
We must always pray to the Lord to tell us what to do, and the Lord will not let us go astray. Adam was not wise enough to ask the Lord about the fruit which Eve gave him, and so he lost paradise. David did not ask the Lord whether it would be a good thing if he took Beth-sheba to wife, and so he fell into the sins of murder and adultery. So with all the saints who sinned: they sinned because they had not called upon God to enlighten and help them. St. Seraphim of Sarov said, ‘When I spoke of myself I was often in error.’
If someone should ask: how am I to pray?, the answer is very simple: fear God. Experience of the fear of God arouses attention and consciousness in the heart and forces it to stand with devotion before God.
Let us then not lose heart, nor be slothful or timid in prayer. Even if we have been brought down to the depths of evil, prayer can speedily draw us back.
You describe how bitterly you regret the inefficacy of your prayers. Beware: to wish for consolation or revelation in prayer is a sure sign of pride. Pray humbly, in perfect simplicity, seeking salvation only through forgiveness, & having faith that God will extend to you His mercy - as He did to the publican.